Researchers have proposed a new way of looking at the brain systems involved in registering bodily sensations. This has key implications for treating depression and other kinds of mental illness.  

Many different brain systems direct our experience of bodily sensations, from a sharp pain in the gut to a broad sense of fatigue. In the past, scientists have thought that such sensations are always responses to signals originating in the peripheral body (outside the brain)—say, bad sushi that creates pain in the gut, or intense heat that causes fatigue.

But in a paper published online May 28th in Nature Reviews Neuroscience, the researchers propose that the relevant brain systems, including the insula and anterior cingulate cortex, are actually making predictions about the way our body is going to feel from moment to moment, rather than simply receiving sensations from the body to stimuli such as food and heat. These predictions are built on our past experience and can be altered by new experiences.

Most importantly, the authors suggest, these predictions can affect sensations by changing the amount of attention we pay to different parts of the body, or how we respond behaviorally to the sensations, in this way increasing or decreasing the related sensations. Disruptions to these prediction systems may contribute to mental illness such as depression, as suggested in research published by 2010 and 2014 NARSAD Young Investigator grantee William Kyle Simmons, Ph.D., of the Laureate Institute for Brain Research, who co-authored this new review paper with Lisa Feldman Barrett, Ph.D.

In prior work, Dr. Simmons and colleagues looked at brain activity in people not taking medication for their depression while those people were directed to focus on sensations related to their heart, bladder, or stomach. During this task, the people with depression showed unusually low activity in the insula, a brain region that processes bodily sensations arriving in the brain via nerves that carry signals about the functioning of the heart, stomach, and bladder. These nerves carry information about hormone levels and immune system activity as well. The low insula activity correlated with higher scores on depression scales, suggesting that irregularities in the insula may actually contribute to depression.

These findings concur with the effectiveness of certain treatments for depression that are known to affect activity in other brain regions (particularly the cingulate cortex) which are also involved in shaping predictions about the body. Targeting part of the brain’s anterior cingulate cortex, the experimental technique called deep brain stimulation, pioneered by Foundation Scientific Council member Helen Mayberg, M.D., often alleviates depression that resists more common forms of treatment. Cognitive behavioral therapy, another effective treatment, is also known to change activity in the cingulate cortex, and may work by altering the predictions that this region makes about the causes of sensations in the body. Simmons and Feldman’s theory, then, points toward treatments that affect the systems for predicting bodily sensations.

Future study, the researchers suggest, should more closely examine how breakdowns in this system may contribute to other conditions associated with disrupted bodily experiences, including autism, eating disorders, and anxiety.

Read the abstract.